The Mitsubishi circuit breakers (MCCB) provide adjustable trip current, branch circuit short circuit and
overcurrent protection, and CANNOT be used to provide motor overLOAD protection.
A MCCB (Mitsubishi/MOLDED CASE CIRCUIT BREAKER) is not the same as a MCP (GV/Motor Circuit Protector)
or MPCB (Motor Protection Circuit Breaker).
Molded case circuit breakers (MCCBs) provide branch and feeder short circuit, ground fault, and
circuit overcurrent protection, they do not provide motor overLOAD protection.
Motor Protection Circuit Breakers (MPCBs/MCPs) are application-specific variations of the MCCB, these breakers
combine the short circuit and isolation functionality of the MCCB with the motor overcurrent protection
of a traditional overload relay. These devices are traditionally used in two component starter applications,
with a contactor to control a motor load. Alternatively they can even be used individually as a manual starter,
although this application is not normally suggested for Molded Case versions of the MPCB due to their limited
mechanical life. MPCBs are UL 489 Listed as circuit breakers and are also UL 508 Listed as motor overload relays.
However, in North America, the Schneider GV motor circuit protectors CANNOT be used as circuit breakers, and would
require 1 circuit breaker (MCCB) upstream from the 3 GV motor protectors (to provide the 3 motor group branch short
circuit and overcurrent protection). The GV motor protectors DO provide adjustable motor overLOAD protection.
The controller and overload devices must be UL listed for group installation.
You would need one circuit breaker (Mitsubishi or other/or time delay fuses) feeding the 3 Schneider GV (or other type)
motor circuit protectors. The feeder CB rated at - (1.25 X FLA (LARGEST MOTOR) + FLA (M2) + FLA (M3)).
Feeder breaker (size) rating selection example;
This assumes that the circuit breaker selected has a voltage
rating equal or greater than the application and that the
interrupting rating is equal or greater to the available short
circuit current. The EXAMPLE panel contains a main feeder breaker
supply with three motor branch circuits.
In this example, the feeder is supplying a 3 phase 3-motor system
at a voltage of 480V.
• Motor 1 is 10 Hp. Current value from Table 430.250
of the NEC is 14 A.
• Motor 2 is 5 Hp. Current value from Table 430.250
of the NEC is 7.6 A.
• Motor 3 is 5 Hp. Current value from Table 430.250
of the NEC is 7.6 A.
Current calculation is:
Motor 1 (14 A* 1.25) 17.5 A
Motor 2 7.6 A
Motor 3 7.6 A
Total 32.7 A
Since the total load comes to 32.7 A and there is not a
commercially available breaker available for 32.7 A, the NEC
allows the next largest standard-sized breaker to be used.
Therefore, a 35A MCCB (molded case circuit breaker) could
be selected to protect this control panel. This circuit breaker
provides branch circuit (feeder) short circuit and overcurrent
protection, but does not provide individual motor overload
protection. Note: each motor branch would also need protection,
and could be provided by a properly rated Schneider GV motor
circuit protector (MCP).